Frank E. Talke

Measurement and Simulation of Partial Contact at the Head/Tape Interface

Partial contact at the head/tape interface is investigated as a function of changes in the head/tape spacing due to asperity compression during contact. A model of head/tape contact, based on measurements of average contact pressure versus average head/tape spacing, is developed and incorporated into a numerical simulation of the head/tape interface. Numerical calculations of head/tape spacing with partial contact are verified by interferometric measurements

The effect of slider surface texture on flyability and lubricant migration under near contact conditions

Abstract Magnetron sputtering and ion beam sputtering were used to texture the air-bearing surface of magnetic recording sliders. Flying height measurements and Laser-Doppler interferometry were used to compare the ‘flyability’ of textured and untextured sliders. Lubricant redistribution on the disk surface caused by slider/disk interactions was investigated using scanning ellipsometry (Surface Reflectance Analyzer (SRA)). The results show that slider surface texture causes only small changes in the flying height of sliders but reduces slider in-plane and out-of-plane vibrations. Textured sliders were found to cause less lubricant depletion on the disk surface than untextured sliders under ‘near contact’ conditions.

Effects of air bearing stiffness on a hard disk drive subject to shock and vibration

A finite element model of a hard disk drive (HDD) is developed to investigate the transient response of an operational HDD subject to shock and vibration. The air bearing stiffness of the head disk interface is determined from a finite element solution of the Reynolds equation and approximated with linear springs. The structural response is analyzed for several types of sliders with a wide range of air bearing stiffness. Results show the response of the head-disk interface subject to shock and the modes excited by vertical and lateral vibrations of the HDD.

An Efficient Finite Element-Based Air Bearing Simulator for Pivoted Slider Bearings using Bi-Conjugate Gradient Algorithms

A computationally efficient air bearing simulator-for pivoted slider bearings has been developed that is based on finite element theory and uses bi-conjugate gradient algorithms in conjunction with a sparse matrix storage scheme. The air bearing simulator involves the simultaneous solution of the Reynolds equation and the slider equilibrium equations. The highly nonlinear problem requires the repeated solution of a nonsymmetric system of equations, typically with a large number of unknowns depending on the complexity of the slider geometry. Iterative solvers, such, as the bi-conjugate gradient algorithms used for this study, require significantly less core memory as compared to direct solvers and reduce the solution time if combined with a suitable preconditions. Of the bi-conjugate gradient algorithm/preconditioner combinations implemented, the Bi-CGSTAB algorithm combined with an ILU preconditioner provided the best performance in terms of smooth convergence and computational efficiency. Presented as a ...

A Model for the Effect of Humidity on Stiction of the Head/Disk Interface

A model has been developed for the effect of humidity on stiction of the head/disk interface. The model combines the meniscus force of the adsorbed water film at the interface with the Greenwood-Williamson surface model, and takes into account the effects of suspension load as well as surface roughness and material properties of both the head and the disk. It correctly predicts the trend for stiction vs. relative humidity as obtained from experimental data. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 8–10, 1990

Effect of humidity on stiction and friction of the head/disk interface

The effect of humidity on the frictional behavior of the head/disk interface is investigated. Experimental results show that stiction and friction are strongly affected by humidity, surface roughness, the presence of a lubricant film on the disk surface, and dwell time. Ellipsometric measurements indicate that the adsorbed water film on a disk surface grows nonlinearly with humidity, suggesting that the films are a major factor in causing stiction at high humidity. >

Axisymmetric motion of radially polarized piezoelectric cylinders used in ink jet printing

An analysis of the low frequency response of piezoelectric squeeze tubes used in drop-on-demand ink jet printing is carried out. The displacements at inner and outer boundaries are determined as a function of voltage and fluid pressure. The results are used to obtain fluid pressure per applied voltage as a function of inner and outer radius. Numerical computations area carried out for PZT-5H, and results are presented in graphical form which can be used to optimize design dimensions. The effect of finite electrode thickness is also studied.

Investigation of Slider Vibrations Due to Contact With a Smooth Disk Surface

The dynamic behavior of pico sliders is investigated during slider-disk contacts as a function of velocity, pitch angle, crown height, and lubricant thickness using laser Doppler vibrometry and acoustic emission sensors. Analog and digital filtering methods are applied to distinguish air bearing and slider body resonances from frequencies related to disk runout, load beam design, and gimbal structure. Sliders with high pitch angle and small crown were found to exhibit smaller vibration amplitudes after slider-disk contacts than sliders with low pitch angle or large crown. The lubricant thickness of the disk was found to affect both the glide avalanche height of the disk and the dynamic behavior of the slider. The results show that roll and pitch frequencies of the air bearing increase with decreasing disk velocity.

A tightly coupled numerical foil bearing solution

Equations describing the steady-state flying height of magnetic tape over a recording head are solved using an algorithm that incorporates a linearized approximation of air bearing stiffness into the tape equation. The one-dimensional infinitely wide equations include compressibility and slip flow in the air bearing, as well as tension, momentum, and flexural rigidity in the tape. The stiffness coupling between the equations allows simulation of complicated head geometries and reduces the computational effort required to determine the steady-state flying height by more than an order of magnitude compared to previously published methods which are based on time-dependent equations. Two example problems are presented, both of which were solved on a personal computer in under one minute. >

Interferometric measurement of disk/slider spacing: the effect of phase shift on reflection

In an interferometric system for measurement of spacing between a transparent disk and a slider, the effect of phase shift on reflection off the slider surface must be considered to obtain an accurate measurement. Here, a theoretical treatment of the problem is described and typical measurements are provided of phase shift on reflection for several types of slider materials in use today. The technique used to measure phase shift utilizes an ellipsometric measurement of the sliders complex index of refraction from which the phase shift on reflection is calculated. Monochromatic interferometric theory is used to show that assuming the slider to behave as a dielectric with a phase shift on reflection of pi can result in flying height measurement errors on the order of 12 nm. The magnitude of the phase-shift effect is investigated for different slider materials. In addition, the variation in phase shift as a function of the wavelength of light is investigated. >